If your device freezes or hangs, you may need to close programs or reset the device to regain functionality. If your device is frozen and unresponsive, press and hold for 8-10 seconds until the SAMSUNG logo appears (see picture). The device will reboot automatically.

If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select Settings → Privacy → Factory data reset → Reset phone→ Erase everything.